Semiconductor devices which output digitized signals are, for example, analog/digital converters (AD converters). A digitized signal is understood as meaning a signal which was generated by digitizing analog signals and which is a digital signal having multiple values.
A Fast Fourier Transformation (FFT) is often used when testing AD converters, as described in IEEE Std 1241-2000. The FFT is also used when testing semiconductor devices which output analog signals as a test response. In this case, the analog test response is digitized before evaluation by means of an FFT.
In an FFT, all spectral components of a signal are calculated at the same time. In a normal FFT with 4096 points, 4096 spectral components are calculated even if, for example, only 10 spectral components from a fundamental tone and nine harmonics are requested. This signifies unnecessary computation complexity which increases the test costs. The spectral components are determined from the FFT during isolated subsequent processing and not while the test response is being received.
One difficulty when starting production of a semiconductor device which outputs analog or digitized test responses is that the test response comprises a large volume of data. During the production test, the test responses are assessed only to determine whether or not the semiconductor device satisfies the test requirements. When production of a semiconductor device is started for the first time, it is not yet known which errors will cause failures. If a semiconductor device fails, test passes will thus be carried out once again in an analysis laboratory in order to find the cause of the error and thus to diagnose the semiconductor device. The data which are obtained during this first test, the production test, cannot be used for the diagnosis since the volume of data is too large to store.